Cities go dark for 'Earth Hour'

Lights will go out across major cities as part of this year's Earth Hour observances.

It's something of a voluntary rolling blackout: Communities around the globe are going dark for an hour on Saturday evening as part of an initiative called "Earth Hour," to raise awareness of climate change.

In more than 7,000 cities and towns across the planet, millions of residents are turning off their lights for an hour from 8:30 to 9:30 p.m. local time to show their environmental concern.